STM investigation on Interplay between Superstructures and Defects in Fe intercalated TaS₂

Hou-Ju Chen^1*, Hung-Kai Huang¹, Po-Hsi Huang¹, Li-Yuan Chen¹, Chia-Nung Kuo², Chin Shan Lue², Minn-Tsong Lin^1,3,4

¹Department of Physics, National Taiwan University, Taipei, Taiwan
²Department of Physics, National Cheng Kung University, Tainan, Taiwan
³Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
⁴Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan

* Presenter:Hou-Ju Chen, email:gooopusgle@gmail.com

Iron-intercalated transition metal dichalcogenides Fe_xTaS₂ exhibit complex electronic behaviors arising from the interplay between intercalated Fe atoms and the TaS₂ host layers. In this study, we employ low-temperature scanning tunneling microscopy and spectroscopy (STM/STS) to investigate how Fe-induced superstructures influence local electronic properties and defect behavior in metallic Fe_xTaS₂. High-resolution STM images reveal well-defined superstructures with bias-dependent contrasts and slight asymmetry, indicating variations in the local electronic states associated with Fe ordering. Various types of point defects, including sulfur vacancies and Fe-related defects, are identified and exhibit distinct topographic and spectroscopic signatures. Statistical analysis shows that these defects preferentially appear at specific sites within the superstructure, suggesting a correlation between the defect formation energy and the periodic potential landscape. Furthermore, the electronic contrast and apparent morphology of defects are strongly affected by the surrounding superstructure, implying that periodic charge modulation alters the local density of states near defect sites. This study provides microscopic insight into how structural ordering and local disorder jointly determine the electronic landscape in metallic Fe_xTaS₂. This project is financially sponsored by National Science and Technology Council (NSTC 112-2112-M-002-046-MY3)

Keywords: Defect, Intercalation, Transition Metal Dichalcogenide, Scanning Tunneling Microscopy